The present disclosure is related to virtual machines and in particular to provisioning services when virtual machines are deployed on a virtualization platform.
Computing environments comprising virtual machines (VMs) are becoming increasingly common. Typically, a virtualization platform provides a hardware infrastructure and a software infrastructure for deploying and administering large configurations of virtual machines. Techniques for describing virtual machines are known. An industry standard for configuring virtual machines is the Open Virtualization Format (OVF). The OVF specification, entitled “Open Virtualization Format Specification,” Document Number DSP0234, Version 1.1.0 (Jan. 1, 2010), published by Distributed Management Task Force, Inc. (DMTF), describes the packaging and distribution of software to be run in virtual machines, and is incorporated herein by reference in its entirety for all purposes. The OVF format is described in a white paper entitled “Open Virtualization Format White Paper,” Document Number DSP2107, Version 1.0.0 (Feb. 6, 2009), published by DMTF, and is incorporated herein by reference in its entirety for all purposes.
Virtual machines may form a complex computing environment and have dependencies among themselves and on the platform they operate on. The OVF specification provides a mechanism for specifying some of those dependencies, including the virtual hardware (e.g., CPU, controllers, Ethernet devices, and so on) and virtual disks that constitute a virtual machine.
The OVF specification defines a virtual appliance as a collection of one or more virtual machines that provide a service. For example, the VMware vSphere® 4.0 software operates a virtualization platform that can manage virtual appliances, referred to as a “vApp” in the VMware vSphere® software environment. For instance, a customer relationship management (CRM) solution may be provided as a vApp that contains a database server VM, an application server VM, and a web server VM, packaged into an OVF package. A vApp, therefore, can express some level of dependency between virtual machines by grouping related virtual machines together and defining startup order semantics.
The computing environment of an enterprise typically involves a large collection of interoperating computing systems. Virtualization provides a platform to facilitate the management of multiple computing systems in the form of virtual machines. The OVF specification and the idea of virtual appliances provide a starting point for managing dependencies among the many virtual machines that may comprise an enterprise computing environment. However, as the size of the computing environment grows, so does the number of dependencies. The ability to formally express platform dependencies with OVF is limited, and so handling large dependencies in a complex computing environment becomes increasingly inefficient. vApps, for example, allow a developer to express that the virtual machines of a multi-tiered solution depend on each other at an abstract level, but a vApp does not allow the developer to express how the virtual machines depend on each other or how they depend on the virtualization platform.